It is known to provide throttle shafts of the aforedescribed construction to permit the controlled discharge of pent-up water, e.g. sewage or waste water, to downstream units for the processing or handling of the sewage. In practice, therefore, it is often required to provide increased flows of dammed-up water, albeit at constant rates, to apparatus downstream of the store of water. Such downstream apparatus can include, for example, for a waste-water-handling installation, a clarifier, a pumping station, the main drainage ditch, or the like.
When a float-controlled throttle flap is used at the respective downstream unit it is not possible with one and the same throttle shaft to feed the different quantities of water which may be needed at the different units.
Thus, since the clarifier, pumping station drainage system and like elements may have different maximum flow requirements Q.sub.max, these different units cannot be fed with the same throttle shaft.
However, each such unit must be operated at a respective substantially constant flow rate and nevertheless should not have its Q.sub.max exceeded. Hence it is common practice to provide a respective throttle shaft at the inlet to each unit, the throttle shafts being differently constructed or of different dimensions in accordance with the respective Q.sub.max. This, of course, is disadvantageous since the throttle shafts must be designed in each instance for the desired Q.sub.max, or a large number of preconstructed throttle shafts must be available in a variety of capacities to accommodate different requirements of the flow rate Q.sub.max.